Biomass is a natural cellulose raw material and is considered to be the most valuable and abundant renewable resource on the earth. In China, the annual yield of natural cellulose biomass is more than 700 million tons, of which corn cobs and stalks represent more than 30%. Biomass is rich in nutritional value and comprises useful chemical components. Although it is widely used in industry, agriculture and animal husbandry, more than 50% of the biomass is not being used. Presently in China, there is a lack of comprehensive measures in the efficient use of biomass such as corn cobs and stalks, often resulting in serious air pollution, which is also an important factor for frequent haze phenomenon and high concentration of fine particles smaller than particle pollution (PM) 2.5 in air. Although China is in the forefront of the world in the deep processing of biomass and has been successful in the exploitation, development and comprehensive utilization of plant stalks, if the use of biomass waste residue is unreasonable, secondary pollution will also be caused to the environment.
In recent years, graphene materials have a wider range of applications in the field of energy and environment, mainly because two-dimensional graphene has large specific surface area, excellent electronic conductivity, and can also be used as additives for resins and rubbers, which can improve physical properties of those materials to meet the needs in different areas. Currently, there are two mainly used methods for synthesizing graphene: chemical vapor deposition (CVD) and reducing graphite oxide. Graphene produced by the CVD method is suitable for use in electronic devices, but it usually requires harsh reaction conditions, expensive equipment, longer period, and has a lower yield, and thus CVD is not suitable for large-scale applications similar to those in the field of electrode materials. The reducing graphite oxide method requires an amount of strong oxidizing agent (e.g. concentrated sulfuric acid, potassium permanganate, etc.) which is roughly 12-fold the amount of the graphite raw material, resulting in serious environmental pollution. Production cost thereof remains high, thus greatly limiting the industrialization of the reducing graphite oxide method.
In summary, these existing graphene preparation methods have problems such as complicated process, poor production safety, high production cost, complicated reaction equipment, harsh reaction conditions, and low yield and others, making it difficult to achieve industrial production with existing methods. Accordingly, the present inventors have studied an alternative method capable of overcoming the above-mentioned obstacles and allowing the synthesis of high-quality biomass grapheneusing cellulose as a raw material that is low in cost, high in yield, high in production safety, highly controllable in the dimensions and physical properties of graphene, and more suitable for industrialized production than the existing methods.